Bottom Line:
Genomewide analyses of distances between orthologous gene pairs from the ascidian species Ciona intestinalis and Ciona savignyi were compared with those of vertebrates.Combining this data with a detailed and careful use of vertebrate fossil records, we estimated the time of divergence between the two ascidians nearly 180 My.This estimation was obtained after correcting for the different substitution rates found comparing several groups of chordates; indeed we determine here that on average Ciona species evolve 50% faster than vertebrates.

ABSTRACTGenomewide analyses of distances between orthologous gene pairs from the ascidian species Ciona intestinalis and Ciona savignyi were compared with those of vertebrates. Combining this data with a detailed and careful use of vertebrate fossil records, we estimated the time of divergence between the two ascidians nearly 180 My. This estimation was obtained after correcting for the different substitution rates found comparing several groups of chordates; indeed we determine here that on average Ciona species evolve 50% faster than vertebrates.

Mentions:
The graphical representation of the relationship between genomic divergence and time of divergence, in vertebrates only, has been presented in Figure 1. A clear linear relationship (i.e., molecular clock) was found, in good agreement with the conclusion achieved by likelihood-based method [11].

Mentions:
The graphical representation of the relationship between genomic divergence and time of divergence, in vertebrates only, has been presented in Figure 1. A clear linear relationship (i.e., molecular clock) was found, in good agreement with the conclusion achieved by likelihood-based method [11].

Bottom Line:
Genomewide analyses of distances between orthologous gene pairs from the ascidian species Ciona intestinalis and Ciona savignyi were compared with those of vertebrates.Combining this data with a detailed and careful use of vertebrate fossil records, we estimated the time of divergence between the two ascidians nearly 180 My.This estimation was obtained after correcting for the different substitution rates found comparing several groups of chordates; indeed we determine here that on average Ciona species evolve 50% faster than vertebrates.

ABSTRACTGenomewide analyses of distances between orthologous gene pairs from the ascidian species Ciona intestinalis and Ciona savignyi were compared with those of vertebrates. Combining this data with a detailed and careful use of vertebrate fossil records, we estimated the time of divergence between the two ascidians nearly 180 My. This estimation was obtained after correcting for the different substitution rates found comparing several groups of chordates; indeed we determine here that on average Ciona species evolve 50% faster than vertebrates.